While I admit to being very new to Perl - I find default/pre-defined variables to be a source of constant inspiration. Using $_ $@ $| etc. can really confuse things.
Oh yeah - and overuse $_ - superfluously if possible - as an example from my first attempt I submitted today:

When putting a smiley right before a closing parenthesis, do you:

Use two parentheses: (Like this: :) )
Use one parenthesis: (Like this: :)
Reverse direction of the smiley: (Like this: (: )
Use angle/square brackets instead of parentheses
Use C-style commenting to set the smiley off from the closing parenthesis
Make the smiley a dunce: (:>
I disapprove of emoticons
Other